Are e-cigarettes a 'gateway' to teen smoking? A new study investigates

A study at 10 Los Angeles high schools has linked e-cigarettes with later tobacco use. Though it does not prove that vaping is a "gateway" to smoking traditional cigarettes, members of the U.S. medical community raised concerns. (Frank Franklin II / Associated Press)

Although teenage smoking rates have plunged in recent decades, teen use of electronic cigarettes has been rising for the last few years. A new study involving more than 2,500 students at 10 Los Angeles schools has found that teens who had used e-cigarettes were far more likely than their peers to start smoking traditional cigarettes and other combustible tobacco products.

Though they don't establish a causal link, the findings published in the Journal of the American Medical Assn. have reignited the debate about whether the potential benefits of e-cigarettes as a smoking cessation tool outweigh the risk that the devices will get more young people hooked on tobacco.

"These findings further indicate that e-cigarette use by our nation's youth, which is a major concern in itself, may also be a gateway to smoking," American Heart Assn. Chief Executive Nancy Brown said in a statement. She called the study results "extremely worrisome."

Electronic cigarettes heat a liquid laced with nicotine and other chemicals to generate a vapor that can be inhaled. That method, known as vaping, may well be less dangerous than inhaling smoke from traditional tobacco products, which contain chemicals known to cause cancer. But it will take time for scientists to assess the long-term health effects of vaping.

"E-cigarettes raise many questions for which there are few answers," Dr. Nancy Rigotti, director of the Tobacco Research and Treatment Center at Massachusetts General Hospital, wrote in an editorial that accompanied the study. "The evidence base is limited because e-cigarettes entered the marketplace without being regulated as either drugs or devices."

The concern that e-cigarettes could act as a "gateway device" is a serious one, since nearly 90% of adult cigarette smokers first started smoking before age 18, according to the Centers for Disease Control and Prevention.

One recent study showed that the number of high school smokers tripled from 2013 to 2014, and another showed that teens who vaped also smoked regular cigarettes.

But such studies have looked at snapshots of these two behaviors, not watched to see how they change over time.

So for the new study, a team led by researchers at USC's Keck School of Medicine tracked the behavior of 2,530 students attending L.A. high schools. The scientists focused on ninth-graders, since "the first year of high school is a vulnerable period for initiating risky behaviors," the study authors wrote.

Although none of the students said they had smoked traditional cigarettes when the study began, 222 had already tried e-cigarettes.

When the researchers followed up with the freshmen six months later, they found that 30.7% of students who had tried e-cigarettes before the study began had gone on to try combustible tobacco products (including cigars and using a hookah). Meanwhile, only 8.1% of those who hadn't used e-cigarettes at the start of the study had smoked tobacco at the six-month mark.

The same pattern was seen after 12 months.

The findings show a link between the two habits, but not a cause. That means it's possible that there's some other underlying factor that might be contributing to both behaviors. Further research will be needed to determine whether vaping truly increases the risk of smoking, the study authors said.

Regardless, experts said, children shouldn't be using e-cigarettes at all. But many e-cigarette products appear to be marketed to youths, they added.

"Knowing the long-term consequences of tobacco use, it is mind-boggling to think that anyone would assume e-cigarette use is acceptable among children, when for many it can function as an entry drug," Dr. Kim Allan Williams, president of the American College of Cardiology, said in a statement.

Brown of the American Heart Assn. urged the federal government to follow through on its pledge to regulate the products.

"These findings are yet another wake-up call to the Food and Drug Administration (FDA) that final regulations are needed now to protect our kids from tobacco," she said.

The study nearly coincided with a report released by Public Health England that concluded that e-cigarettes are 95% less harmful than traditional cigarettes and could be used to help smokers kick the habit.

The review from the British government-funded agency also said it was "erroneous" to label e-cigarettes as a gateway to smoking.

"We strongly suggest that use of the gateway terminology be abandoned until it is clear how the theory can be tested in this field," wrote the authors of the 111-page report. "Nevertheless, the use of [e-cigarettes] and smoking requires careful surveillance in young people."